Kingdom [Animalia] Linnaeus, 1758 - animals
   Ecdysozoa Aguinaldo, Turbeville, Linford, Rivera, Garey, Raff & Lake 1997, nom. cl. inval. - ecdysozoans see Clade Ecdysozoa Aguinaldo, Turbeville, Linford, Rivera, Garey, Raff & Lake 1997 [Lake, Halanych, Servin & Garey 2020]
     Panarthropoda Nielsen, 1995 - panarthropods
       Tritocerebra see [unranked] Tactopoda Budd, 2001
         Phylum Arthropoda Siebold, 1848 - arthropods
           Subphylum Arachnomorpha Heider, 1913 see [unranked] Arachnomorpha Heider, 1913
             Infraphylum Cheliceriformes
               Superclass Chelicerata Heymons, 1901 see Subphylum Chelicerata Heymons, 1901
                 Epiclass Euchelicerata Weygoldt & Paulus, 1979 see [unranked] Euchelicerata Weygoldt & Paulus, 1979
                   Class Xiphosura Latreille, 1802 - horseshoe crabs